Electric furnace.



E. WEINTRAUB.

ELEGTRIG FURNACE.

APPLICATION FILED MAY 13, 1908. RENEWED FEB. 23, 1911. 99%882, PatentedJuly 11,1911.

2 SHEETS-SHEET l.

Fig.1.

\ l 5 l i /2 f Witnesses: Inventor E. WEINTRAUB.

ELECTRIC FURNACE.

APPLICATION FILED MAY13,1908. RENEWED FEB. 23,1911.

Patented. July 11, 19M.

2 SHEETSFSHEET 2.

Inventor Ezechiel Weitraub,

Watnesses: %-M

UNITED PATENT OFFICE.

EZECHIEL WEINTRAUB. 0F LYNN, MASSACHUSETTS. ASSIGNOR T0 GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented. July 1 1, m1 1.

Original application filed July 2, 1906, Serial No. 324,399. Divided andthis application filed May 18, 1908,

Serial No. 432,565.

To all whom it may concern:

Be it known that I, Eznomnn VVEIN'IRAUB, a citizen of the United States,residing at Lynn, county of Essex, State of Massachusetts, have inventedcertain new and useful Improvements in Electric Furnaces, (division ofmy application. Serial No. 324,399, filed July 2. 1906,) of which thefollowing is a specification.

This invention relates to the heat treatment of refractory materials bymeans of an arc in a vacuum. In carrying out my invention, I use thematerial to be melted or treated as an electrode in a vacuum arc furnaceand I pass sutllcient current through the are to sinter or even to meltdown the refractory material under treatment. The appa 'atus whereby Icarry out this process is hereinafter described and includes variousnovel means and arrangements whereby the heating action of the arc maybe concentrated on the electrode and whereby the general treatment maybe eflectively and rapidly carried on.

I may apply my method to the fusion or purification of the morerefractory metals such as tungsten, thorium, osmium, etc., by pressingup rods from the powdered metal and using them as anodes in a mercuryare.

In order that the means for carrying out my invention may be betterunderstood, reference should be had to the drawings forming a part ofthis specification, in which Figure 1 is a view of one form of vacuumfurnace suitable for the melting of tungsten and other refractorymetals, and Fig. 2 is a modified form of furnace particularly adaptedfor the use of high current.

The vacuum furnace shown in Fig. 1 comprises an evacuated envelop 1 ofglass or other suitable material provided With a mercury cathode 2 and acondensing chamber 3 located thereabove and also provided with a lateralextension 1 opening into an anode chamber 5. This anode chamber containsa relatively large body of mercury 6 and is closed at the bottom by arubber cork 7. A rod 8 of the material to be melted or sintered by theheat of the arc is cemented or otherwise secured to a suitable lead-wire9 projecting through the rubber cork. Before starting the operation, Ipre- Renewed February 23, 1911.

Serial No. 610,389.

fer to have the level of the mercury in the anode chamber only slightlylower than the upper end of the stick to be treated as I find that withsuch an arrangement the heating action of the arc is concentrated on theend of the stick, and the latter may be readily fused down. The level ofthe mercury may be controlled by a stop cock 10 connecting with a wastemercury chamber 11 so that af ter the end of the refractory stick hasbeen melted I may gradually draw off the mercury and thus cause theheated zone to gradually travel down the stick. The mercury at all timescovers up the lead wire and prevents contact of the arc therewith. Theproduct resulting from the high heat treatment above described is aglobulc of the metal fused or sintered by the heating action of the arcand substantially free from volatile impurities. As the rod 8 may bepressed or molded out of one of the metals ordinarily obtained only in apowdered form, the above treatment serves to consolidate and otherwisechange the metal under treatment.

To facilitate the starting of the mercury arc, I provide the apparatuswith an auxiliary mercury anode 12 connected to the cathode andreceiving direct current through a suitable circuit 13, and by thismeans I am able, by slightly shaking the tube to establish an arc to themercury cathode 2 and thereby start the main arc.

The main heating current is preferably a direct current and may besupplied by a suitable dynamo 14 and may be controlled by a rheostat 15or other regulating mechanism. As the current is likely to be high, Iprefer to provide the mercury cathode 2 with a plurality of leading-inwires, to diminish the likelihood of rupturing the glass because of theheating action of the current. I prefer to provide the cathode With aplatinum Wire 16 projecting slightly above the surface of the mercury asI find that this arrangement diminishes the total quantity of mercuryvaporized from the cathode and consequently prevents an abnormalquantity of mercury vapor from cooling the anode by contact therewith.

In the operation of the furnace, I find that the metal stick undertreatment carries Substantially all the current, or in other words, thatthe mercury body surrounding the stick does not become anode withrespect ,to the cathode of the tube. This phenomenon I attribute to thedifference in the polarization of a mercury surface and of a solidanode, the polarization of the solid material'being less than that ofmercury; consequently the stick under treatment acts as anode to theexclusion of the surrounding mercury.

If desired, the apparatus may be cooled, either by an air blast or byWater circulation.

Fig. 2 shows a modification adapted for the transmission of especiallyheavy currents. It comprises an evacuated envelop 17 provided at the topwith a rubber stopper 18 from which is suspended a cathode cup 19 ofsilica, alumina or other non-conductive and refractory material. Thiscup is filled with mercury and is connected with a power circuit bymeans of a mercury column 20 inclosed in a tube the lower end of whichis pierced by a plurality of lead-wires 21. The rubber stopper 18 alsocarries a glass tube 22 in which is supported an auxiliary anode 23 toserve as a starting means. This starting is effected by opening a stopcock 24: at the upper end of the tube 22 and permitting mercury to rundown from a funnel 25 and momentarily establish contact between theauxiliary anode 28 and the mercury cathode and thereby complete thecircuit through a resistance 26 to a suitable source of current. Themain anode of the furnace is at the lower end of the chamber andconsists of a rod 27 of pressed metal or other material to be treated.It is surrounded by a body of mercury 28 which communicates with theopen air through a barometric column 29. A suitable source of directcurrent 30 is connected between the anode and the cathode and thegeneral heating operation is effected in the same manner as with theapparatus shown in Fig. 1. By supporting the cathode in a silica cupwell removed from the walls of the vessel, it is impossible for the arcto come in contact with the glass, and I am thereby enabled to run thecurrentdensity to a very high value without danger of cracking theenvelop.

Although I have referred to mercury as a suitable material forestablishing a heating arc, I also contemplate the use of amalgams andsimilar alloys, vaporizable at the operating temperature of the furnaceand chemically inert with respect to the material under treatment.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. A vacuum furnace comprising a substantially exhausted envelop, acathode therein, an anode of compressed powder in fixed relation to saidcathode, means for rendering conductive the space between said anode andcathode to establish a heating are therein, and means for concentratingthe heating action of-said are on a limited portion of said anode.

2. A vacuum furnace comprising a sealed envelop, a cathode therein ofvaporizable metal, means for producing an are from said cathode, and afurnace charge supported in fixed position relative to said cathode andoperative as anode for the heating are.

3. A vacuum furnace comprising an exhausted envelop, a cathode therein,a body of material to be structurally changed supported -in fixedposition relative to said cathode but separated therefrom, and meansforionizing the space between said cathode and said material to start anare therethrough.

4. In a furnace, the combination of an exhausted envelop, a liquidcathode therein, a body of compressed refractory metal powder mounted infixed relation to said cathode, and means for initiating and maintainingan arc to said powder of a magnitude sufficient to melt it into ahomogeneous body.

5. A vacuum furnace comprising an envelop, a removable closure for saidenvelop carrying the charge to be heated, a mercury cathode, and meansfor establishing and maintaining a mercury-vapor are between saidcathode and said charge of a magnitude sufficient to fuse said charge.

6. A vacuum furnace comprising an envelop, a removable closure for saidenvelop carrying a furnace charge in the form of a stick of compressedrefractory metal powder, a cathode at a distance from said charge, andmeans for establishing an arc betwee said cathode and said charge.

7. In a furnace, the combination of an envelop, a mercury cathodetherein, means for starting an arc to. said cathode, means forsupporting a furnace charge to be treated, and means for concentratingthe heating action of said are on a limited portion of said furnacecharge.

8. In a furnace, the combination of an evacuated envelop, a liquidcathode therein, means for starting an arc to said cathode, a' furnacecharge supported in fixed position With respect to said cathode andconstituting an anode therefor, and a liquid protecting a part of saidanode from the heating action of the are between said cathode and anode.

9. In a furnace, the combination of an evacuated envelop, a cathodetherein, a furnace charge, means for establishing an are between saidcathode and said charge, means for protecting a part of said charge fromthe heating action of said are, and means for withdrawing saidprotective means to progressively expose said furnace charge totreatment by said are.

10. In a furnace, the combination of an evacuated envelop, a mercurycathode therein supported remote from the wall of said envelop, meansfor supporting a furnace charge as anode for said cathode, means forestablishing a mercury are between said anode and cathode, andprotective means for said furnace charge progressively removable toexpose said charge to the heating action of said arc.

EZECHIEL WVEINTRAUB.

\Vitnesses:

JOHN A. MoMANUs, J r.,

CHARLES A. BARNARD.

